Mrs. Ernest wants to know how much light her daisies need. She places one pot of daisies under a sunlamp and another pot of daises on a windowsill. Each day she gives both plants the same amount of water. Which term BEST describes the amount of water given to the plants each day?

Control Variable

Explanation:

A control variable is a variable that is held constant throughout the cause of an experiment, in order to test accurately the relationship between the dependent and the independent variables. The control variable, which is amount of water needed by the plants in this case, has the property of affecting the growth of the daisies, hence if it is not held constant, the result of the experiment might not be accurately attributed to the light source alone.

Therefore, to say with certainty that the difference seen in both categories of plants was from the difference in lighting alone, other variables (amount of water, type of soil, temperature etc.) has to be held constant

i believe the answer would be:

d. violin, clarinet, french horn, and tuba